Stumped... Mycar is an '85 K-Jetronic-equipped 8v, completely standard, 69K mileswarranted from new. Normally it runs beautifully, pulls strongly and returns OK fuel economy (about 26mpg according to the MFA). If I try to hot-start it, it requires throttle to catch, and then stumbles and eventually stalls if not revved to 3000rpm and held there for a few seconds. It sounds like it's misfiring during that period. After that, it runs beautifully, although the idle can get a bit lumpy after a while instop-start traffic. I'm new to K-Jet; anybody got any idea what's going on? Cheers
You should be getting more MPG than that, I'm sure up to 40mpg is achievable, 35 at least? Could be the blue temp sensor and/or an air leak somewhere.
he's going off the mpg, and we all know how correct they are! there isn't a blue temp sensor on k-jet. you have to be care i tihnk with misfires/backfires as it can move the sensor plate which will make it hard starting. if you have a multimeter and a haynes, check the wur and the wiring to it. will it drive and get warm and drive fine? but play up once its been turned off and back on?
Ah yes the Multi Function OF LIES Could it be the WUR is switching on when it shouldn't or perhaps the acumilator not keeping residual pressure? Not sure about the acumilator as surely pressure would build up very quickly and not cause problems for a few seconds... Edited by: rubjonny
This sounds like classic fuel vapourization. Heat soak in the engine bay when you switch off boils the fuel in the injector lines causing air locks. The missing you hear on start up is the lines bleeding themselves. Does your fan after run work?
Cheers for the replies! Yes, the fan overrun works, but it's only ever cut-in once, and then only after some bad-mood spirited driving. Once it's got over its hiccups, it smoothes-out a treat and runs very well. The stumbling is a bit random; sometimes it'll fire without any throttle, then stumble until revved but not stall; other times it'll stall straight away. It sounds like it's trying to run on two or three cylinders until I rev it, then it fires on all four and runs smoothly. Once it'srunning it's faultless (until you stop and try to restart...). It'sa bit betternow I'm back on Super Unleaded; I had to tank-up last time with 95 RON Premium unleaded, as no local garage had any Super. We're a bit backward, us Northeners. Does that help?
Still sounds like fuel vapourization, it might be worth changing the fan after run switch. Do you have a tubular (4 branch) ex manifold?
Hi, Could be a leaky injector - can you smell petrol in your oil ? Could be a failed one way valve on the end of the fuel pump. Could be your coil is not putting out a fat enough spark, are your leads, dissy cap, plugs etc spot on ? If it is something wrong with the fuel side of things then it is all fairly easy to check as long as you have access to a in-line pressure meter. K-Jet is a very clever mechanical injection system - a simple methodical approah will find the problem quickly. Dare I ask the question as to whether the fuel filler neck has ever been replaced ? The root of all MK1 evils :-((
The one way valve is called the fuel pump check valve. You are loosing pressure out of the system some where and in my experience it will either be the check valve or leaky injectors - best way to tell for sure is to get a gauge and measure the pressures. If you relly want to get in to the k-jet system then the book "How to tune and modify Bosch Fuel Injection" by Ben Watson is a top guide.
cause mine is having the same simptoms, only on cold starts. hot starts are one crank and there we go! but miss firing, and stuff on cold...
Thats not so likely to be fuel vapourisation, that's more likely a leaking cold start injector or loss of system pressure.
the cold start injector, is disconcted(the blue plug) and what can cause loss of system pressure!? i had the black box where the fuel pump is knackered, but replaced, and its fine now...
Sussed it! I had the car dyno'd at Mikeanics in Congleton (highly recommended btw). Mike traced the problem to leaking injector seals. It was also running lean (which can't have helped matters), so as a bonus I now have more power and torque; 109.9bhp and 109.1 lbf ft. Thanks for all the advice
You'll get better economy as well as it would have been running really lean with injector seals leaking as well.
ok, i have a hard time starting my k'jet 8v when its cold....it won't do it unless you put full throttle on then turn the key
